DESCRIPTION The goal of the proposed study is to identify and understand the function of genes involved in color vision. Zebrafish will be the animal model, and the approach will be to identify and characterize "color-blind" animals using the optokinetic response. The first mutant identified by this method, pob, lacks red cones by 5 days post-fertilization. At 3 days, however, photoreceptors expressing red opsin are present, suggesting that red- sensitive cones form initially but later disappear. Many interesting issues about the mutation cannot be addressed that red-sensitive cones form initially but later disappear. Many interesting issues about the mutation cannot be addressed because the mutant dies by day 9. Microdissection techniques are being utilized to transplant the embryonic eye anlage of the mutant into a wild-type embryo in order to obtain a non-lethal mutation model system. The cone mosaic in juvenile and adult fish will be characterized to determine whether the pob mutation causes: the normal cone photoreceptor pattern within the mosaic to be disrupted, other photoreceptors to degenerate, and, photoreceptor cell regeneration in response to the photoreceptor death. Additional color-blind mutants will be screened for, isolated and characterized histologically and electrophysiologically. These studies will further our understanding of the molecular mechanisms underlying color vision within the vertebrate retina and establish candidates for the search of gene products involve din human retinal degeneration.